1.Field of the Disclosure
The embodiments described herein relate to a method and system to enable the re-stimulation through means of hydraulic fracturing of horizontal multizone wellbores. The method and system uses wellbore plugs that may be comprised of various combinations of proppants, and ultra-lightweight proppants, and lightweight fillers, and polymers. The plugs may be used to hydraulically isolate portions of a wellbore during the re-fracturing treatment process.
2. Description of the Related Art
Natural resources such as gas and oil may be recovered from subterranean formations using well-known techniques. For example, a horizontal wellbore may be drilled within the subterranean formation. After formation of the horizontal wellbore, a string of pipe, e.g., casing, may be run or cemented into the wellbore. Hydrocarbons may then be produced from the horizontal wellbore.
In an attempt to increase the production of hydrocarbons from the wellbore, the casing is perforated and fracturing fluid is pumped into the wellbore to fracture the subterranean formation. The fracturing fluid is pumped into the wellbore at a rate and a pressure sufficient to form fractures that extend into the subterranean formation, providing additional pathways through which reservoir fluids being produced can flow into the wellbores. The fracturing fluid typically includes particulate matter known as a proppant, e.g., graded sand, ceramic proppant, bauxite proppant, or resin coated sand, that may be suspended in the fracturing fluid. The proppant pumped into the fractures serves to form a permeable pack that “props” the fractures open after the pressure exerted on the fracturing fluid during the hydraulic fracturing process has ended and the fractures close onto the proppant.
A production zone within a wellbore may have been previously fractured, but the prior hydraulic fracturing treatment may not have adequately stimulated the formation leading to insufficient production results. Even if the formation was adequately fractured, the production zone may no longer be producing at desired levels. Over an extended period of time, the production from a previously fractured horizontal multizone wellbore may decrease below a minimum threshold level. Techniques used to increase the hydrocarbon production from an existing wellbore include the re-fracturing of the existing casing perforations, and the addition of new perforations in the casing from which new fractures into the subterranean formation can be propagated. Of concern is the problem faced due to the multiple open fractures that already exist within the horizontal wellbore from previous hydraulic fracturing stimulation treatments. The ability to isolate the targeted casing perforations ensures that the fracturing fluid pumped into the wellbore enters the formation at its intended point within the horizontal lateral. To accomplish this, the re-fracturing treatment of a horizontal wellbore is designed to be pumped down a string of coiled tubing, or a string of smaller jointed pipe known as tubing. The temporary setting of an isolation tool known as a packer near the end of the tubular pipe then isolates all of the open perforations along the annulus between the wellbore casing and the smaller diameter coiled tubing, or tubing string. Expandable tubulars or cladding procedures have been used within a wellbore in an attempt to block the flow path of the fracturing fluid into old fractures, so as to promote the formation of new fracture clusters. The use of expandable tubulars or cladding may not adequately provide the desired results and further, may incur too much expense in the effort to increase production from the wellbore. A more efficient way to increase the production of a horizontal wellbore is needed.